One of the primary energy consumers in your heating system is the furnace blower motor. The same holds true for the air conditioner blower located in the air handler. Yet, when published efficiency ratings for new furnaces and air conditioners are computed in the laboratory, the efficiency of the blower motor isn’t included in the calculation. Therefore, homeowners who opt to upgrade to a new furnace or A/C yet keep the old-school, inefficient blower motor may discover they don’t receive the efficiency gains they expected based on the published ratings. Upgrading to a furnace ECM motor when you renew your system avoids that disappointment, as well as the higher utility costs that come with it.
On many installed furnaces, the original (OEM) blower motor is a PSC model. Short for permanent split capacitor, PSC motors are designed to do what furnace motors have always done in the past: simply turn on and off. The output of a PSC motor isn’t controllable and it has no intermediate speeds. It’s either running at full output or it’s not running at all. The energy consumption of the motor is therefore fixed at a single maximum rate.
Electronically commutated motors (ECM) represent an advance in blower motor efficiency that saves substantial energy and improves aspects of overall system performance. ECMs are brushless motors developed by General Electric, which owns the trademark on the name. Since its introduction in 1985, the adoption of ECM technology has played a major role in increasing the energy efficiency of furnaces and air conditioners.
Here are some of the advantages to upgrading to a furnace ECM motor instead of sticking with the original equipment PSC model:
- Variable speeds – Unlike an on/off PSC motor, a furnace ECM motor can operate at a range of outputs between zero and 100 percent. Output of the motor can be adjusted by signals from a controller, or permanently programmed to advance through a range of speeds during each on cycle of the furnace. A typical HVAC program signals the motor to ramp up speed gradually in it’s first stage—a more energy-efficient mode than simply turning on at full speed. The motor slowly reaches a maximum output appropriate for the specific thermostat setting and then incrementally decreases output to transition into what’s known as a soft stop instead of an abrupt off.
- Energy savings – An ECM delivers efficiencies in the range of 65 or 75 percent, depending on the output. An PSC motor, on the other hand, has efficiencies of only about 45 percent. While the upfront cost of an ECM is higher than replacing a conventional PSC unit, the expected savings in operating costs will eventually offset the price difference.
- Lower maintenance and longer life – ECMs utilize true ball bearings that reduce or eliminate the need for lubrication. The gradual ramp-up to maximum output and gentle soft stops reduce stress and wear and tear on motor components. ECMs are also less prone to overheating. In general, an ECM installed in a typical HVAC application should deliver about 90,000 hours, or the equivalent of 10 years of service. A PSC motor has an expected service life of only 50,000 hours or eight years before replacement is required.
- Increased comfort – Because a furnace ECM motor runs a longer cycle at a lower output most of the time, heating and cooling is more consistent and rooms avoid the temperature spikes and sags common with on/off PSC blowers. When a furnace turns completely off, a layer of rising hot air accumulates at the ceiling and doesn’t provide warmth to occupants at ground level. The longer, low-output cycles of an ECM blower break up the stratification of heat at the ceiling and keep warm air circulating throughout the room.
- Better air quality – The air filters in your furnace and air conditioning system require airflow in the ducts to be effective. Once airflow stops during the off cycle of a PSC-equipped blower, all air filtration ceases as well. During these periods, airborne particulates have a chance to accumulate in living spaces. Because an ECM unit maintains longer periods of air circulation in the ducts at lower output, more effective filtration and healthier indoor air quality results.
- 2013 tax credit – The $150 federal tax credit for furnaces with an AFUE of at least 95 can be increased to $200 if the blower motor is upgraded to a variable speed ECM model. This credit expires on December 31, 2013.
For information about upgrading to a furnace ECM motor in the Baltimore area, contact Griffith Energy Services Inc. today.
Written by Kevin Spain